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If x2 – 2xy = 84 and x – y = –10, what is the value of |y|?
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23 Jun 2018, 11:52
23 Jun 2018, 11:52
2
Expert Reply
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Question Stats:
87% (01:21) correct
12% (02:57) wrong based on 74 sessions
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Re: If x2 – 2xy = 84 and x – y = –10, what is the value of |y|?
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25 Jun 2018, 07:00
25 Jun 2018, 07:00
Ans. 4
Re: If x2 – 2xy = 84 and x – y = –10, what is the value of |y|?
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28 Jul 2018, 16:11
28 Jul 2018, 16:11
1
Expert Reply
Explanation
One of the “special products” you need to memorize for the exam is \(x^2 – 2xy + y^2 = (x – y)^2\).
Write this pattern on your paper and plug in the given values:
\(x^2 - 2xy + y^2 = (x - y)^2\)
\(84 + y^2 = (-10)^2\)
\(84 + y^2 = 100\)
\(y^2 = 16\)
\(y = 4\) or \(-4\), so \(|y| = 4\).
One of the “special products” you need to memorize for the exam is \(x^2 – 2xy + y^2 = (x – y)^2\).
Write this pattern on your paper and plug in the given values:
\(x^2 - 2xy + y^2 = (x - y)^2\)
\(84 + y^2 = (-10)^2\)
\(84 + y^2 = 100\)
\(y^2 = 16\)
\(y = 4\) or \(-4\), so \(|y| = 4\).
